Method and device for processing HARQ feedback in a mobile communication system

ABSTRACT

A device and method for handling HARQ feedback in a mobile communication system are disclosed. The HARQ feedback handling method includes: analyzing a control message from a base station to recognize presence of HARQ feedback relationships between downlink carriers and uplink carriers; determining an uplink carrier (a downlink carrier) to support HARQ feedback in response to downlink traffic (uplink traffic) sent through a downlink carrier (an uplink carrier); and sending (receiving) HARQ feedback through the determined uplink carrier (downlink carrier).

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 13/499,741, filed on May 15, 2012, which is a U.S. National Stageapplication under 35 U.S.C. § 371 of an International application filedon Oct. 1, 2010 and assigned application number PCT/KR2010/006717, whichclaimed the benefit of a Korean patent application filed on Oct. 1, 2009in the Korean Intellectual Property Office and assigned Serial number10-2009-0094004, of a Korean patent application filed on Jan. 19, 2010in the Korean Intellectual Property Office and assigned Serial number10-2010-0004800, and of a Korean patent application filed on Mar. 16,2010 in the Korean Intellectual Property Office and assigned Serialnumber 10-2010-0023470, the entire disclosure of each of which is herebyincorporated by reference.

TECHNICAL FIELD

The present invention relates to a device and method for handling HARQfeedback in a mobile communication system and, more particularly, to adevice and method for handling HARQ feedback for a user equipmentutilizing multiple aggregated carriers.

BACKGROUND ART

In general, mobile communication systems have been developed to providecommunication services to users in motion. Thanks to rapid technologicaladvancement, mobile communication systems are capable of providing notonly voice communication services but also high-speed data communicationservices.

Recently, 3GPP has been working to standardize specifications for theLong Term Evolution (LTE) system, which is regarded as a next generationmobile communication system. The LTE system is expected to becommercially available in 2010, and aims to realize high-speed packetbased communication supporting a data rate of 100 Mbps exceedingexisting data rates. With completion of LTE system standardization, toachieve higher data rates, 3GPP started to develop the LTE-Advanced(LTE-A) system by introducing various new communication schemes to theLTE system.

Carrier aggregation (CA) is a representative one of the communicationschemes to be newly introduced. Unlike an existing user equipment thatuses one downlink carrier and one uplink carrier for data transmissionand reception, a user equipment supporting carrier aggregation may usemultiple downlink carriers and multiple uplink carriers. To supportcarrier aggregation involving multiple downlink carriers and multipleuplink carriers, some functions of the user equipment (UE) and the basestation (Node B) must be changed. The HARQ (hybrid automatic repeatrequest) scheme is one of such functions. In HARQ, when data is receivedfrom a base station, a user equipment may perform error correctionoperation on the received data and detect errors using a simple schemelike cyclic redundancy check (CRC) to determine necessity ofretransmission. If retransmission is necessary, the user equipment sendsa retransmission request to the base station through the uplink channel.However, in the event that carrier aggregation involving multiplecarriers is employed, it is necessary to determine, in response totraffic having received through one carrier, another carrier throughwhich HARQ feedback is to be sent.

DISCLOSURE OF INVENTION Technical Problem

The present invention is to provide a method and device that enable auser equipment using multiple aggregated carriers to report uplink powerheadroom in a mobile communication system.

Solution to Problem

According to a first embodiment of the present invention, an HARQfeedback handling method in a mobile communication system may include:analyzing a control message from a base station to recognize presence ofHARQ feedback relationships between downlink carriers and uplinkcarriers; and sending, when the PDCCH of a first downlink carrier isused to carry downlink resource allocation information for a seconddownlink carrier, uplink HARQ feedback on an uplink carrier having anuplink feedback relationship with a downlink carrier on which PDSCHtransmission is performed.

According to a second embodiment of the present invention, an HARQfeedback handling method in a mobile communication system may include:analyzing a control message from a base station to recognize presence ofHARQ feedback relationships between downlink carriers and uplinkcarriers; and sending, when a first downlink carrier is used to carryresource allocation information of a second downlink carrier, HARQfeedback through an uplink carrier having an uplink feedbackrelationship with a downlink carrier on which the resource allocationinformation is received.

According to a third embodiment of the present invention, an HARQfeedback handling method in a mobile communication system may include:analyzing a control message from a base station to recognize presence ofHARQ feedback relationships between downlink carriers and uplinkcarriers; and receiving, when the PDCCH of a downlink carrier is used tocarry uplink resource allocation information for an uplink carrier,downlink HARQ feedback on a downlink carrier on which the uplinkresource allocation information is received.

According to a fourth embodiment of the present invention, an HARQfeedback handling method in a mobile communication system may include:analyzing a control message from a base station to recognize presence ofHARQ feedback relationships between downlink carriers and uplinkcarriers; and receiving, when the PDCCH of a downlink carrier is used tocarry uplink resource allocation information for an uplink carrier,downlink HARQ feedback on a downlink carrier having a downlink feedbackrelationship with an uplink carrier on which uplink traffic is sent.

According to a fifth embodiment of the present invention, an HARQfeedback handling method in a mobile communication system may include:recognizing an uplink HARQ feedback relationship between downlinkcarriers and uplink carriers; and sending, when PDSCH reception isperformed through semi-persistent transmission resources, uplink HARQfeedback through an uplink carrier having an uplink feedbackrelationship with a downlink carrier on which PDSCH reception isperformed.

According to a sixth embodiment of the present invention, an HARQfeedback handling method in a mobile communication system may include:recognizing a downlink carrier to receive downlink feedback at the timeof configuring semi-persistent transmission resources; and receiving,when PUSCH transmission is performed through semi-persistenttransmission resources, downlink HARQ feedback through the downlinkcarrier recognized at the time of configuring semi-persistenttransmission resources.

According to a seventh embodiment of the present invention, an HARQfeedback handling method in a mobile communication system may include:recognizing mappings between downlink carriers and uplink carriers; andreceiving, when PUSCH transmission is performed through semi-persistenttransmission resources, downlink HARQ feedback on a downlink carrierassociated in path loss with an uplink carrier on which the PUSCHtransmission is performed.

According to an eighth embodiment of the present invention, an HARQfeedback handling method in a mobile communication system may includereceiving, when PUSCH transmission is performed through semi-persistenttransmission resources, HARQ feedback on a downlink carrier throughwhich a signal activating the semi-persistent transmission resources hasbeen received. In the method, after receiving a signal activatingsemi-persistent transmission resources through the PDCCH, the userequipment periodically performs PUSCH transmission through the activatedsemi-persistent transmission resources. When performing PUSCHtransmission through separate semi-persistent transmission resources,the user equipment receives HARQ feedback on a downlink carrier throughwhich a signal activating the semi-persistent transmission resources hasbeen received.

According to a ninth embodiment of the present invention, an HARQfeedback handling method in a mobile communication system may include:performing PUSCH transmission on an uplink carrier; and receiving HARQfeedback on a downlink carrier selected according to the same criterionregardless of whether the uplink transmission is conducted throughtransmission resources dynamically allocated by the PDCCH or throughsemi-persistent transmission resources.

According to another embodiment of the present invention, an HARQfeedback handling device for a user equipment in a mobile communicationsystem may include: a transceiver unit performing uplink transmissionand downlink reception to and from a base station; a control messagehandler determining a downlink carrier to receive downlink feedback onthe basis of a control message received by the transceiver unit; acontrol unit controlling the transceiver unit to receive uplink resourceallocation information and to send uplink data according to the uplinkresource allocation information; and an HARQ feedback carrier determinercontrolling the transceiver unit to receive, in response to uplinktransmission performed under control of the control message handler andthe control unit, downlink HARQ feedback through a downlink carrier thatis used to receive the uplink resource allocation information.

Advantageous Effects of Invention

In a mobile communication system employing carrier aggregation, a userequipment using multiple downlink and uplink carriers can perform HARQoperation without errors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an LTE system architecture.

FIG. 2 illustrates a hierarchy of wireless protocols in the LTE system.

FIG. 3 illustrates carrier aggregation in the LTE system.

FIG. 4 illustrates a resource configuration for HARQ feedback in the LTEsystem.

FIG. 5 illustrates an uplink HARQ feedback relationship between downlinkcarriers and uplink carriers in the LTE system.

FIG. 6 illustrates a downlink HARQ feedback relationship between uplinkcarriers and downlink carriers in the LTE system.

FIG. 7 is a sequence diagram for identifying uplink and downlink HARQfeedback relationships using a carrier aggregation message.

FIG. 8 illustrates provision of uplink HARQ feedback according to afirst embodiment of the present invention.

FIG. 9 is a flowchart illustrating UE operation according to the firstembodiment of the present invention.

FIG. 10 illustrates provision of uplink HARQ feedback according to asecond embodiment of the present invention.

FIG. 11 is a flowchart illustrating UE operation according to the secondembodiment of the present invention.

FIG. 12 illustrates provision of downlink HARQ feedback according to athird embodiment of the present invention.

FIGS. 13A and 13B illustrates UE operation according to the thirdembodiment of the present invention.

FIG. 14 illustrates provision of downlink HARQ feedback according to afourth embodiment of the present invention.

FIG. 15 is a flowchart illustrating UE operation according to the fourthembodiment of the present invention.

FIG. 16 is a flowchart illustrating UE operation according to a fifthembodiment of the present invention.

FIGS. 17A and 17B illustrates UE operation according to a sixthembodiment of the present invention.

FIGS. 18A and 18B illustrates UE operation according to a seventhembodiment of the present invention.

FIG. 19 is a flowchart illustrating UE operation according to an eighthembodiment of the present invention.

FIG. 20 is a flowchart illustrating UE operation according to a ninthembodiment of the present invention.

FIG. 21 is a block diagram of the user equipment according to anotherembodiment of the present invention.

MODE FOR THE INVENTION

Hereinafter, exemplary embodiments of the present invention will bedescribed with reference to the accompanying drawings.

Embodiments of the present invention relate to a method and device thatenable a user equipment using multiple aggregated carriers to reportuplink power headroom.

A base station may assign a greater number of carriers to a userequipment employing carrier aggregation, and the user equipment may sendand receive data by simultaneously using multiple carriers. This maycorrespond to a case where the user equipment sends and receives data toand from multiple cells in parallel. Hence, the maximum data rate mayincrease in proportion to the number of aggregated carriers, and theuser equipment may perform data transmission at a significantly higherrate. In a mobile communication system employing carrier aggregation,embodiments of the present invention relate to a method and device thatenable a user equipment utilizing multiple downlink carriers andmultiple uplink carriers to determine, in response to traffic receivedon a first carrier, a second carrier on which HARQ feedback is to besent.

In addition, embodiments of the present invention relate to a mappingbetween traffic and HARQ feedback when cross carrier scheduling, inwhich resource allocation information and traffic are sent on differentcarriers, is employed in particular. Embodiments of the presentinvention relate further to a method for controlling uplink feedbacktransmission and downlink feedback reception according tosemi-persistency of transmission resources.

In the present invention, nine embodiments are provided as follows.

The first embodiment of the present invention provides a method fordetermining, when cross scheduling among downlink carriers is conducted,an uplink carrier supporting uplink HARQ feedback. In the method of thefirst embodiment, when the PDCCH of a first downlink carrier is used tocarry downlink resource allocation information for a second downlinkcarrier, the uplink HARQ feedback is sent on an uplink carrier having anuplink feedback relationship with a downlink carrier on which PDSCHtransmission is performed.

In the second embodiment of the present invention, when the PDCCH of afirst downlink carrier is used to carry downlink resource allocationinformation for a second downlink carrier, the uplink HARQ feedback issent on an uplink carrier having an uplink feedback relationship with adownlink carrier on which PDCCH reception is performed. In other words,when a first downlink carrier is used to carry PDSCH schedulinginformation of a second downlink carrier, the user equipment sendsfeedback through an uplink carrier having an uplink feedbackrelationship with a downlink carrier on which resource allocationinformation is received.

The third embodiment of the present invention provides a method fordetermining, when cross scheduling among uplink carriers is conducted, adownlink carrier supporting downlink HARQ feedback. In the method of thethird embodiment, when the PDCCH of a downlink carrier is used to carryuplink resource allocation information for an uplink carrier, thedownlink HARQ feedback is sent on a downlink carrier on which the uplinkresource allocation information is sent.

The fourth embodiment of the present invention provides a method fordetermining, when cross scheduling among uplink carriers is conducted, adownlink carrier supporting downlink HARQ feedback. In the method of thefourth embodiment, when the PDCCH of a downlink carrier is used to carryuplink resource allocation information for an uplink carrier, thedownlink HARQ feedback is sent on a downlink carrier having a downlinkfeedback relationship with an uplink carrier on which uplink traffic issent.

In the fifth embodiment of the present invention, when PDSCHtransmission and reception is performed through semi-persistenttransmission resources without PDCCH operation, the user equipment sendsHARQ feedback through an uplink carrier having an uplink feedbackrelationship with a carrier on which PDSCH reception is performed.

The sixth embodiment of the present invention provides a method fordetermining, when PUSCH transmission is performed throughsemi-persistent uplink transmission resources, a downlink carriersupporting downlink HARQ feedback. In the method of the sixthembodiment, when PUSCH transmission is performed through semi-persistenttransmission resources, the user equipment receives downlink HARQfeedback through the PDCCH of a downlink carrier preset at the time ofconfiguring semi-persistent transmission resources.

The seventh embodiment of the present invention provides a methodwherein, when PUSCH transmission is performed through semi-persistenttransmission resources, HARQ feedback is received on a downlink carrierassociated in path loss with an uplink carrier in which thesemi-persistent transmission resources are configured.

The eighth embodiment of the present invention provides a methodwherein, when PUSCH transmission is performed through semi-persistenttransmission resources, HARQ feedback is received on a downlink carrierthrough which a signal activating the semi-persistent transmissionresources has been received. After receiving a signal activatingsemi-persistent transmission resources through the PDCCH, the userequipment periodically performs PUSCH transmission through the activatedsemi-persistent transmission resources. When performing PUSCHtransmission through separate semi-persistent transmission resources,the user equipment receives HARQ feedback on a downlink carrier throughwhich a signal activating the semi-persistent transmission resources hasbeen received.

The ninth embodiment of the present invention provides a method wherein,when PUSCH transmission is performed on an uplink carrier, the userequipment receives HARQ feedback on a downlink carrier selectedaccording to the same criterion regardless of whether the uplinktransmission is conducted through transmission resources dynamicallyallocated by the PDCCH or through semi-persistent transmissionresources.

Before a description of the embodiments (the first to ninth embodiments)of the present invention, the architecture and operation of the LTEmobile communication system employing carrier aggregation are describedwith reference to FIGS. 1, 2 and 3. FIG. 1 illustrates an LTE systemarchitecture.

Referring to FIG. 1, an LTE radio access network is composed of basestations (Evolved Node B, Node B, or ENB) 105, 110, 115 and 120, amobility management entity (MME) 125, and a serving-gateway (S-GW) 130.A user equipment (UE) 135 may connect to an external network through theENBs 105 to 120 and the S-GW 130.

The ENBs 105 to 120 correspond to Node Bs of the UMTS system. The ENB isconnected to the user equipment 135 through a wireless channel, and mayperform more complex functions in comparison to the existing Node B. Inthe LTE system, as all user traffic including real-time services likeVoIP (Voice over IP) services is served by shared channels, it isnecessary to perform scheduling on the basis of status informationcollected from user equipments. Each of the ENBs 105 to 120 performsthis scheduling function. In most cases, a single ENB controls multiplecells. To achieve a data rate of up to 100 Mbps, the LTE system utilizesorthogonal frequency division multiplexing (OFDM) in a 20 MHz bandwidthas radio access technology. The LTE system employs adaptive modulationand coding (AMC) to determine the modulation scheme and channel codingrate according to channel states of a user equipment. The S-GW 130provides data bearers, and creates and removes a data bearer undercontrol of the MME 125. The MME 125 performs various control functions,and is connected to multiple ENBs.

FIG. 2 illustrates a hierarchy of wireless protocols in the LTE system.

Referring to FIG. 2, in the LTE system, the wireless protocol stack iscomposed of a PDCP (Packet Data Convergence Protocol) layer 205 or 240,an RLC (Radio Link Control) layer 210 or 235, a MAC (Medium AccessControl) layer 215 or 230, and a physical (PHY) layer 220 or 225. ThePDCP layer 205 or 240 performs compression and decompression of IPheaders. The RLC layer 210 or 235 reconfigures PDCP PDUs (Protocol DataUnit) to a suitable size to conduct ARQ operations. The MAC layer 215 or230 is connected to multiple RLC layer devices in a user equipment, andmultiplexes RLC PDUs into MAC PDUs or demultiplexes MAC PDUs into RLCPDUs. The physical layer 220 or 225 converts higher layer data into OFDMsymbols by means of channel coding and modulation and transmits the OFDMsymbols through a wireless channel, or converts OFDM symbols receivedthrough a wireless channel into higher layer data by means ofdemodulation and channel decoding and forwards the data to higherlayers. At the transmitting side, for a given protocol layer, an SDU(Service Data Unit) refers to a unit data that the protocol layer inputsfrom a higher layer, and a PDU refers to a unit data that the protocollayer outputs to a lower layer.

FIG. 3 illustrates carrier aggregation in the LTE system.

Referring to FIG. 3, one ENB 305 transmits and receives signals throughmultiple carriers across multiple frequency bands. For example, assumethat the ENB 305 uses a carrier 315 with a center frequency fl and acarrier 310 with a center frequency f3. A user equipment not supportingcarrier aggregation uses one of the two carriers 310 and 315 to send andreceive data. A user equipment 330 having a carrier aggregationcapability may use multiple carriers including the carriers 310 and 315in parallel to send and receive data. Here, the ENB 305 may assign twoor more carriers to the user equipment 330 having a carrier aggregationcapability according to service conditions, increasing the data rate ofthe user equipment 330. In a traditional sense, it may be consideredthat one cell is formed of a downlink carrier and an uplink carrierprovided by the same base station. In carrier aggregation, a userequipment may be considered as sending and receiving data throughmultiple cells in parallel. Hence, the maximum data rate of the userequipment may be increased in proportion to the number of aggregatedcarriers.

The present invention relates to a method and device that enables a userequipment, which performs communication using multiple downlink carriersand multiple uplink carriers in a communication system providingmultiple downlink carriers and multiple uplink carriers, to determine,for traffic received on a first carrier, a second carrier on which HARQfeedback is to be sent. In particular, the present invention relates toa mapping between traffic and HARQ feedback when resource allocationinformation and traffic are sent on different carriers (cross carrierscheduling).

FIG. 4 illustrates a mapping between traffic and HARQ feedback when asingle carrier is used.

In FIG. 4, the x-axis indicates time and the y-axis indicatesfrequencies. When a user equipment uses a downlink (DL) carrier and anuplink (UL) carrier, HARQ feedback for data traffic received on onecarrier is sent on the other carrier. HARQ feedback transmissionresources are reserved in given regions in advance. The downlink carrierincludes a PDCCH (physical downlink control channel) 405 acting as acontrol region to carry control information such as downlink controlinformation (DCI) and HARQ feedback, and a PDSCH (physical downlinkshared channel) 410 acting as a control region to carry downlink data.

The PDCCH 405 is composed of transmission resources including controlchannel elements (CCE) to carry DCI, and DL A/Ns (Ack/Nack). DCI may bedownlink or uplink resource allocation information, and may be sentthrough one or more CCEs. Although one downlink carrier may includedozens of CCEs per 1 msec, only six CCEs are shown in FIG. 4 for ease ofdescription. One CCE is mapped to one UL A/N transmission resource. Forexample, CCE #2 415 is mapped to UL A/N #2 420. Ack/Nack for downlinktraffic related to downlink resource allocation information sent throughCCE #2 415 is sent through UL A/N #2 420 mapped with CCE #2 415. Theuplink carrier includes the same number of UL A/N transmission resourcesas the number of CCEs present in the paired downlink carrier.

The PDSCH 410 includes a plurality of downlink resource blocks (RB).Downlink resource allocation information sent to a user equipmentcontains information on downlink resource blocks allocated to the userequipment, and downlink traffic is sent and received through the PDSCH.

The uplink carrier is composed of UL A/N transmission resources and aPUSCH (physical uplink shared channel) 425 to send uplink traffic. ThePUSCH 425 includes a plurality of uplink resource blocks, each of whichis mapped to one DL A/N transmission resource. For example, uplink RB #1430 is mapped to DL A/N #1 435. In other words, Ack/Nack for uplinktraffic sent through RB #1 430 is sent through DL A/N #1 435 mapped withRB #1 430.

In FIG. 4, a user equipment uses a pair of a downlink carrier and anuplink carrier. A description is given of transmission resources of theuplink carrier that are used to transmit uplink HARQ feedback inresponse to downlink traffic received on the downlink carrier. Adescription is also given of transmission resources of the downlinkcarrier that are used to transmit downlink HARQ feedback in response touplink traffic transmitted on the uplink carrier.

In the case that multiple downlink carriers and multiple uplink carriersare configured for one user equipment supporting carrier aggregation, itis necessary to consider association between traffic and HARQ feedback.A possible solution is to notify the user equipment of a relationshipbetween aggregated downlink and uplink carriers. FIGS. 5 and 6illustrate HARQ feedback relationships in the LTE system employingmultiple downlink and uplink carriers for carrier aggregation.

FIG. 5 illustrates an uplink HARQ feedback relationship between downlinkcarriers and uplink carriers in the LTE system. In FIG. 5, it is assumedthat the user equipment uses three downlink carriers and two uplinkcarriers for carrier aggregation.

When carrier aggregation is utilized, relationships between downlinkcarriers and uplink carriers may be established in advance. In FIG. 5,it is configured in advance so that uplink HARQ feedback for downlinkcarrier 1 505 and downlink carrier 2 510 is transmitted through uplinkcarrier 1 520 and uplink HARQ feedback for downlink carrier 3 515 istransmitted through uplink carrier 2 525. Here, when uplink HARQfeedback for a downlink carrier x is sent through an uplink carrier y,the downlink carrier x and uplink carrier y are defined as having anuplink feedback relationship.

When downlink resource allocation information for the PDSCH of downlinkcarrier 1 505 is transmitted through the PDCCH of downlink carrier 1505, HARQ feedback for the PDSCH of downlink carrier 1 505 istransmitted through uplink carrier 1 520 having an uplink feedbackrelationship.

Likewise, it is necessary to pre-specify a downlink carrier on whichHARQ feedback for uplink traffic sent through the PUSCH of an uplinkcarrier is to be transmitted. FIG. 6 illustrates a downlink HARQfeedback relationship between uplink carriers and downlink carriers inthe LTE system.

In FIG. 6, it is configured in advance so that downlink feedback foruplink carrier 1 620 is transmitted through downlink carrier 1 605 anddownlink feedback for uplink carrier 2 625 is transmitted throughdownlink carrier 3 615. Here, when downlink HARQ feedback for an uplinkcarrier z is sent through a downlink carrier w, the uplink carrier z anddownlink carrier w are defined as having a downlink feedbackrelationship.

The uplink feedback relationship and downlink feedback relationship maybe notified to each user equipment using a call setup message or thelike. FIG. 7 is a sequence diagram for identifying uplink and downlinkHARQ feedback relationships using a carrier aggregation message.

Referring to FIG. 7, the ENB sends a control message indicating carrieraggregation to the user equipment (710). Here, the control message maycontain carrier aggregation information (regarding DL carriers and ULcarriers) coded using information elements illustrated in Table 1. InTable 1, characters ‘>’ and ‘>>’ indicate levels of information, and aninformation element prefixed with ‘>>’ is lower level information of aninformation element prefixed with ‘>’.

TABLE 1 Information element name Single/Multiple Description >DL carrierMultiple (as many as the Information on information number of aggregatedaggregated downlink carriers) downlink carriers >>Carrier identifierSingle Integer identifying carrier >>Center frequency Single Centerfrequency of carrier >>Bandwidth Single Bandwidth supported bycarrier >>UL feedback Single Identifier of UL carrier in carrieridentifier uplink feedback relationship with DL carrier >UL carrierMultiple (as many as the Information on information number of aggregatedaggregated uplink carriers) uplink carriers >>Carrier identifier SingleInteger identifying carrier >>Center frequency Single Center frequencyof carrier >>Bandwidth Single Bandwidth supported by carrier >>DLfeedback Single Identifier of DL carrier in carrier identifier downlinkfeedback relationship with UL carrier

After reception of the carrier aggregation information coded usinginformation elements illustrated in Table 1, the user equipmentidentifies an uplink feedback relationship between downlink carriers anduplink carriers (i.e., an uplink carrier to be used to send uplink HARQfeedback) and identifies a downlink feedback relationship between uplinkcarriers and downlink carriers (i.e., a downlink carrier to be used toreceive downlink HARQ feedback) (715).

Even though feedback relationships are pre-established as describedabove, when the carrier transporting resource allocation information isdifferent from the carrier transporting traffic, the pre-establishedfeedback relationships are not sufficient for determining a carrier thatis to be used for sending or receiving HARQ feedback. For example, whenthe downlink carrier delivering resource allocation information fordownlink traffic is different from the downlink carrier deliveringactual downlink traffic, it is necessary to determine an uplink carrierto deliver HARQ feedback.

Next, according to embodiments of the present invention, a descriptionis given of a method for determining a carrier that is used to deliverdownlink or uplink HARQ feedback in a user equipment supporting carrieraggregation.

First Embodiment

The first embodiment of the present invention provides a method fordetermining, when cross scheduling among downlink carriers is conducted,an uplink carrier supporting uplink HARQ feedback. In the method of thefirst embodiment, when the PDCCH of a first downlink carrier is used tocarry downlink resource allocation information for a second downlinkcarrier, the uplink HARQ feedback is sent on an uplink carrier having anuplink feedback relationship with a downlink carrier on which PDSCHtransmission is performed.

FIG. 8 illustrates provision of uplink HARQ feedback according to thefirst embodiment of the present invention.

Referring to FIG. 8, when scheduling information for PDSCH 830 ofdownlink carrier 1 (DL CC1 805) is sent on downlink carrier 3 (DL CC3815), the user equipment sends feedback (UL ACK/NACK (1) 835) throughuplink carrier 1 (UL CC1 820) having an uplink feedback relationshipwith the downlink carrier on which PDSCH reception is performed.

In the first embodiment of FIG. 8, the base station should performresource scheduling so that uplink feedback transmission resources arenot duplicated. When the PDSCH of a downlink carrier is scheduledsimultaneously by two downlink carriers using the same CCE, a problemthat one or more feedbacks for PDSCH reception are transmitted throughuplink feedback transmission resources of an uplink carrier having anuplink feedback relationship with the PDSCH may arise. For example, whenRB #x of DL CC3 815 is allocated to a first user equipment by means ofCCE #1 of DL CC1 805 and RB #y of DL CC3 815 is allocated to a seconduser equipment by means of CCE #1 of DL CC2 810, the different userequipments may use, to send different feedbacks, an uplink feedbacktransmission resource mapped with CCE #1 among uplink feedbacktransmission resources of UL CC2 825 having an uplink feedbackrelationship with DL CC3 815 delivering downlink traffic. Hence, whenthe method of the first embodiment is applied, the base station shouldperform resource scheduling so as to avoid such a feedback transmissionresource conflict.

FIG. 9 is a flowchart illustrating UE operation for HARQ feedbackaccording to the first embodiment of the present invention.

Referring to FIG. 9, the user equipment identifies an uplink feedbackrelationship between downlink carriers and uplink carriers on the basisof carrier aggregation information coded using information elementsillustrated in Table 1 (905). Namely, the user equipment analyzes thereceived carrier aggregation information to determine an uplink carrieron which uplink feedback for a downlink carrier is to be sent. The userequipment receives PDSCH scheduling information (downlink resourceallocation information) for a downlink carrier through the PDCCH of adownlink carrier (910), and proceeds to steps 915 to 925.

Upon reception of the downlink resource allocation information, the userequipment checks whether cross scheduling is used (915). That is, theuser equipment determines whether the downlink carrier on which thedownlink resource allocation information is received is the same as thedownlink carrier on which downlink traffic is to be sent. When crossscheduling is not used (i.e., the two downlink carriers are the same),the user equipment sends uplink feedback through an uplink carrierhaving an uplink feedback relationship with the corresponding downlinkcarrier (920). When cross scheduling is used (i.e., the two downlinkcarriers are not the same), the user equipment sends uplink feedbackthrough an uplink carrier having an uplink feedback relationship withthe downlink carrier on which downlink traffic is received (925).

Second Embodiment

In the second embodiment of the present invention, when the PDCCH of afirst downlink carrier is used to carry downlink resource allocationinformation for a second downlink carrier, the uplink HARQ feedback issent on an uplink carrier having an uplink feedback relationship with adownlink carrier on which PDCCH reception is performed.

FIG. 10 illustrates provision of uplink HARQ feedback according to thesecond embodiment of the present invention.

Referring to FIG. 10, when scheduling information for PDSCH 1030 ofdownlink carrier 1 (DL CC1 1005) is sent on downlink carrier 3 (DL CC31015), the user equipment sends feedback through uplink carrier 2 (ULCC2 10250) having an uplink feedback relationship with the downlinkcarrier on which resource allocation information is received. In thesecond embodiment, resource conflicts for uplink feedback transmissiondescribed in relation to the first embodiment do not occur. As describedbefore, the uplink feedback transmission resource for downlink trafficis mapped with the CCE through which resource allocation information forthe downlink traffic is transmitted. Hence, resource conflicts foruplink feedback transmission do not arise unless resource allocationinformation is allocated to different user equipments through the sameCCE.

FIG. 11 is a flowchart illustrating UE operation according to the secondembodiment of the present invention.

Referring to FIG. 11, the user equipment identifies an uplink feedbackrelationship between downlink carriers and uplink carriers on the basisof carrier aggregation information coded using information elementsillustrated in Table 1 (1105). Namely, the user equipment determines anuplink carrier on which uplink feedback for a downlink carrier is to besent. The user equipment receives PDSCH scheduling information (downlinkresource allocation information) for a downlink carrier through thePDCCH of a downlink carrier (1110), and proceeds to steps 1115 to 1125.

Upon reception of the downlink resource allocation information throughthe PDCCH of a downlink carrier, the user equipment checks whether crossscheduling is used (1115). That is, the user equipment determineswhether the downlink carrier on which the downlink resource allocationinformation is received is the same as the downlink carrier on whichdownlink traffic is received. When cross scheduling is not used (i.e.,the two downlink carriers are the same), the user equipment sends uplinkfeedback through an uplink carrier having an uplink feedbackrelationship with the corresponding downlink carrier (1120). When crossscheduling is used (i.e., the two downlink carriers are not the same),the user equipment sends uplink feedback through an uplink carrierhaving an uplink feedback relationship with the downlink carrier onwhich the downlink resource allocation information is received (1125).

Third Embodiment

The third embodiment of the present invention relates to a method fordetermining, when cross scheduling among uplink carriers is conducted, adownlink carrier supporting downlink HARQ feedback. In the thirdembodiment, to receive downlink HARQ feedback in response to PUSCHtransmission, when PUSCH transmission is performed according to regularscheduling, the user equipment receives downlink HARQ feedback on adownlink carrier having a feedback relationship with an uplink carrieron which the PUSCH transmission is performed. When PUSCH transmission isperformed according to cross carrier scheduling, the user equipmentreceives downlink HARQ feedback on a downlink carrier through whichdownlink resource allocation information is received.

FIG. 12 illustrates provision of downlink HARQ feedback according to thethird embodiment of the present invention.

Referring to FIG. 12, in the third embodiment of the present invention,when the PDCCH of a downlink carrier is used to carry uplink resourceallocation information for an uplink carrier, the downlink HARQ feedbackis sent on the downlink carrier on which the uplink resource allocationinformation is sent. For example, when resource allocation information(UL scheduling (1) 1230) for the PUSCH of uplink carrier 1 (UL CC1 1220)is sent on downlink carrier 3 (DL CC3 1215), downlink feedback (DLACK/NACK (1) 1235) for PUSCH transmission 1240 through uplink carrier 1(UL CC1 1220) is received on downlink carrier 3 (DL CC3 1215) on whichthe resource allocation information is sent.

In the case of utilizing the method of the third embodiment, as thedownlink carrier used to send resource allocation information for thePUSCH is also used to support downlink HARQ feedback, it is notnecessary to establish a separate downlink feedback relationship,simplifying UE operation. In contrast, the base station should performuplink transmission resource allocation so as not to cause resourceconflicts for downlink feedback transmission. For example, when RB #1 ofUL CC1 is scheduled by DL CC3, feedback is transmitted using a downlinkfeedback transmission resource corresponding to RB #1 of DL CC3. Here,if RB #1 of another uplink carrier is also scheduled by DL CC3, aproblem that the downlink feedback transmission resource is used tocarry feedbacks for two different uplink transmissions is caused. Thebase station should perform scheduling so as not to cause such aproblem.

FIG. 13A is a flowchart for UE operation according to the thirdembodiment of the present invention, and FIG. 13B is a sequence diagramfor an HARQ handling procedure between the user equipment and basestation according thereto.

Referring to FIG. 13B, the ENB sends a control message indicatingcarrier aggregation to the user equipment (1350). Here, the controlmessage contains carrier aggregation information related to downlinkcarriers and uplink carriers aggregated in the user equipment (DLcarrier information and UL carrier information). The carrier aggregationinformation may include information on unique identifiers, centerfrequencies and bandwidths of downlink carriers and uplink carriers, andfeedback relationships between downlink carriers and uplink carriers.After reception of the control message, the user equipment performsdownlink and uplink carrier configuration and monitors the PDCCH of eachdownlink carrier to receive downlink or uplink scheduling information.

The ENB sends uplink resource allocation information (UL grant (crosscarrier scheduling)) for an uplink carrier through a downlink carrier(1355). After reception of the uplink resource allocation information,the user equipment performs PUSCH transmission using allocated uplinktransmission resources on the uplink carrier (1360). To receive downlinkHARQ feedback in response to the PUSCH transmission, the user equipmentmonitors the downlink feedback channel of the downlink carrier on whichthe uplink resource allocation information for the PUSCH transmission isreceived. After reception of PUSCH data from the user equipment, the ENBsends downlink HARQ feedback through the downlink carrier on which theuplink resource allocation information has been sent (1365). That is,the user equipment may perform PUSCH transmission using uplinktransmission resources allocated by the base station, and monitor thedownlink carrier on which uplink resource allocation information isreceived to receive downlink HARQ feedback.

In the third embodiment, when carrier aggregation is employed, HARQfeedback relationships between downlink carriers and uplink carriers maybe configured. Here, an HARQ feedback relationship may be indicated by acommon identifier assigned to paired downlink and uplink carriers. Forexample, for PUSCH transmission through an uplink carrier with anidentifier ‘x’, downlink HARQ feedback may be received through adownlink carrier with an identifier ‘x’. Alternatively, downlink carrierinformation may directly indicate an association between a downlinkcarrier and an uplink carrier. An HARQ feedback relationship is notvalid when uplink transmission resources are allocated through crosscarrier scheduling. Hence, when uplink transmission resources areallocated through cross carrier scheduling, the user equipment receivesHARQ feedback through a downlink carrier that is used to transmit uplinkresource allocation information not through a downlink carrierassociated with the uplink carrier.

In the third embodiment of the present invention, there are twoapproaches to handle downlink HARQ feedback for PUSCH transmission. Inone approach, when PUSCH transmission is conducted according to regularscheduling, the base station sends downlink HARQ feedback through adownlink carrier having a feedback relationship with an uplink carrieron which PUSCH transmission is conducted and the user equipment receivesthe downlink HARQ feedback. In the other approach, when PUSCHtransmission is conducted according to cross carrier scheduling, thebase station sends downlink HARQ feedback through a downlink carrier onwhich resource allocation information is sent and the user equipmentreceives the downlink HARQ feedback.

FIG. 13A illustrates a procedure in which the base station sendsdownlink HARQ feedback through a downlink carrier on which resourceallocation information is sent and the user equipment receives thedownlink HARQ feedback. Referring to FIG. 13A, when the ENB sends uplinkresource allocation information (UL grant (cross carrier scheduling))for an uplink carrier through the PDCCH of a downlink carrier, the userequipment receives the uplink resource allocation information (PUSCHscheduling information) (1305). The user equipment may be aware thatHARQ feedback will be transmitted on a downlink carrier on which PUSCHscheduling information is received. The user equipment performs PUSCHtransmission using uplink transmission resources allocated on theindicated uplink carrier (1310). After reception of the PUSCH data, theENB sends downlink HARQ feedback through the downlink carrier on whichthe uplink resource allocation information is sent. After PUSCHtransmission, the user equipment monitors the downlink carrier on whichthe uplink resource allocation information is received to receive theHARQ feedback for the PUSCH data.

Fourth Embodiment

The fourth embodiment of the present invention relates to a method fordetermining, when cross scheduling among uplink carriers is conducted, adownlink carrier supporting downlink HARQ feedback.

FIG. 14 illustrates provision of downlink HARQ feedback according to thefourth embodiment of the present invention.

Referring to FIG. 14, when the PDCCH of a downlink carrier is used tocarry uplink resource allocation information for an uplink carrier, thedownlink HARQ feedback is sent on a downlink carrier having a downlinkfeedback relationship with an uplink carrier on which uplink traffic issent. For example, when resource allocation information (UL scheduling1430) for the PUSCH of uplink carrier 1 (UL CC1 1420) is sent throughdownlink carrier 3 (DL CC3 1415), downlink feedback (DL ACK/NACK (1)1435) for PUSCH 1440 through uplink carrier 1 (UL CC1 1420) is sentthrough downlink carrier 1 1405 having a downlink feedback relationshipwith uplink carrier 1 (UL CC1 1420).

When the method of the fourth embodiment is utilized, it is necessary toestablish a downlink feedback relationship between a downlink carrierand uplink carrier, but resource conflicts for downlink feedbacktransmission described in relation to the third embodiment do not occur.For example, when RB #1 of UL CC1 is scheduled by DL CC3, feedback istransmitted using a downlink feedback transmission resourcecorresponding to RB #1 of DL CC1. As the downlink feedback transmissionresource is reserved for RB #1 of DL CC1, resource conflicts fordownlink feedback transmission do not occur unless the schedulererroneously assigns RB #1 of DL CC1 to another user equipment.

FIG. 15 is a flowchart illustrating UE operation according to the fourthembodiment of the present invention.

Referring to FIG. 15, the user equipment identifies a downlink feedbackrelationship between downlink carriers and uplink carriers on the basisof carrier aggregation information coded using information elementsillustrated in Table 1 (1505). Namely, the user equipment determines adownlink carrier on which downlink feedback for an uplink carrier is tobe received.

When the ENB sends uplink resource allocation information for an uplinkcarrier through the PDCCH of a downlink carrier, the user equipmentreceives the uplink resource allocation information through the downlinkcarrier (1510). The user equipment transmits uplink traffic on theindicated uplink carrier (1515). The user equipment receives HARQfeedback for the uplink traffic through a downlink HARQ feedbacktransmission resource of a downlink carrier having a downlink feedbackrelationship with the uplink carrier on which the uplink traffic is sent(1520).

In the LTE mobile communication system, as transmission resources aredynamically allocated for packet transmission, one or more pieces ofresource allocation information may be needed to transmit one packet. Asdynamic resource allocation is inefficient for applications such as VoIPrepeatedly generating small packets, the LTE mobile communication systemalso provides a data transmission scheme based on semi-persistenttransmission resources. In semi-persistent scheduling (SPS), onceactivated, the same transmission resources are repeatedly allocated tothe same user equipment at regular intervals without separate resourceallocation information. Under semi-persistent scheduling, as allocatedtransmission resources are valid for a long time, separate resourceallocation information is not necessary. To allocate semi-persistenttransmission resources, the base station sends a semi-persistentresource allocation message through the PDCCH to a user equipment andsends packets to the user equipment using allocated semi-persistenttransmission resources.

Next, a description is given of handling HARQ feedback usingsemi-persistent transmission resources according to the fifth to seventhembodiments of the present invention.

Fifth Embodiment

In the case of downlink semi-persistent transmission resources, afterthe ENB sends a control signal indicting semi-persistent resourceactivation through the PDCCH to the user equipment, PDSCH transmissionis conducted at regular intervals through the activated semi-persistenttransmission resources without downlink resource allocation information.The fifth embodiment of the present invention provides a method whereinwhen PDSCH transmission is performed through semi-persistenttransmission resources without PDCCH operation, the user equipment sendsHARQ feedback through an uplink carrier having an uplink feedbackrelationship with a downlink carrier on which PDSCH transmission isperformed.

FIG. 16 is a flowchart illustrating UE operation according to the fifthembodiment of the present invention.

Referring to FIG. 16, the user equipment identifies an uplink feedbackrelationship between downlink carriers and uplink carriers (1605). Whenthe user equipment receives downlink traffic (i.e., PDSCH reception) ona downlink carrier (1610), it checks whether the PDSCH reception isperformed through semi-persistent transmission resources (1615). Here,PDSCH reception through semi-persistent transmission resources indicatesabsence of PDCCH reception. When the PDSCH reception is performedthrough semi-persistent transmission resources, the user equipment sendsuplink feedback through an uplink carrier having an uplink feedbackrelationship with the downlink carrier on which the PDSCH reception isperformed (1620). When the PDSCH reception is performed through regulardynamic transmission resources (not through semi-persistent transmissionresources), the user equipment sends uplink feedback through an uplinkcarrier having an uplink feedback relationship with a downlink carrieron which PDCCH reception is performed (1625).

As described above, in the fifth embodiment, when PDSCH reception isperformed through semi-persistent transmission resources without PDCCHoperation, the user equipment sends uplink feedback through an uplinkcarrier having an uplink feedback relationship with a downlink carrieron which the PDSCH reception is performed. Otherwise, the user equipmentsends uplink feedback through an uplink carrier having an uplinkfeedback relationship with a downlink carrier on which schedulinginformation is received.

Sixth Embodiment

The sixth embodiment of the present invention relates to a method fordetermining, when PUSCH transmission is performed throughsemi-persistent uplink transmission resources, a downlink carriersupporting downlink HARQ feedback. PUSCH transmission throughsemi-persistent uplink transmission resources indicates absence ofuplink resource allocation information. In the sixth embodiment, whenPUSCH transmission is performed through semi-persistent transmissionresources, the user equipment receives downlink HARQ feedback throughthe PDCCH of a downlink carrier preset at the time of configuringsemi-persistent transmission resources.

FIG. 17A is a flowchart for UE operation according to the sixthembodiment of the present invention, and FIG. 17B is a sequence diagramfor an HARQ handling procedure between the user equipment and basestation according thereto.

Referring to FIG. 17B, the ENB sends a control message indicatingcarrier aggregation to the user equipment (1750). Here, the controlmessage contains carrier aggregation information related to downlinkcarriers and uplink carriers aggregated in the user equipment (DLcarrier information and UL carrier information). The carrier aggregationinformation may include information on unique identifiers, centerfrequencies and bandwidths of downlink carriers and uplink carriers, andfeedback relationships between downlink carriers and uplink carriers.After reception of the control message, the user equipment performsdownlink and uplink carrier configuration and monitors the PDCCH of eachdownlink carrier to receive downlink or uplink scheduling information.

The ENB sends uplink semi-persistent resource allocation informationthrough a downlink carrier to the user equipment (1755). Here, theuplink semi-persistent resource allocation information may containinformation specifying transmission resources to be used for downlinkfeedback (for example, information indicating transmission resources ofthe PDCCH to be used for delivering downlink feedback in response touplink traffic through the uplink semi-persistent transmissionresources: DL CC x; UL SPS resource allocation (HARQ feedback resourceinformation). Here, only transmission resources are indicated, and thedownlink carrier to deliver downlink feedback is not indicated.

After uplink semi-persistent resources are allocated by the ENB, theuser equipment performs uplink transmission at regular intervals throughthe allocated uplink semi-persistent resources (UL CC x: SPStransmission) (1760). For example, after a given time from reception ofthe uplink semi-persistent resource allocation information, the userequipment may perform uplink transmission through the uplinksemi-persistent resources. After uplink transmission, the user equipmentreceives downlink HARQ feedback through a transmission resource of thePDCCH of a downlink carrier identified according to a preset rule(1765). The downlink carrier delivering downlink HARQ feedback inresponse to uplink traffic transmitted through semi-persistenttransmission resources may be the primary carrier or a downlink carrierassociated with an uplink carrier supporting the allocated uplinksemi-persistent transmission resources.

For uplink transmission using dynamically allocated transmissionresources (not semi-persistent transmission resources), the userequipment receives downlink HARQ feedback on a downlink carrier on whichuplink resource allocation information is received. More specifically,the ENB sends uplink resource allocation information for an uplinkcarrier through a downlink carrier (DL CC y: UL grant) (1770), and theuser equipment receives the uplink resource allocation information. Theuser equipment performs uplink transmission using uplink transmissionresources of the uplink carrier (1775). The ENB sends downlink HARQfeedback for PUSCH data through the downlink carrier on which the uplinkresource allocation information has been sent (1780). After PUSCHtransmission, the user equipment monitors the downlink carrier on whichthe uplink resource allocation information is received to receivedownlink HARQ feedback. Here, the dynamically allocated transmissionresources refer to transmission resources allocated according to regularscheduling (not semi-persistent scheduling). The primary carrier is alsoreferred to as the primary cell.

Referring to FIG. 17A, which illustrates UE operation according to thesixth embodiment of the present invention, the user equipment identifiesa downlink carrier that is used to receive downlink feedback in responseto uplink transmission using semi-persistent transmission resourcesduring configuration of semi-persistent transmission resources (1705).Semi-persistent transmission resources are configured according to agiven RRC message. The ENB may send the user equipment an RRC messagecontaining information on the period of semi-persistent transmissionresource allocation and on the downlink carrier to deliver downlinkfeedback for uplink transmission using semi-persistent transmissionresources. Instead of a message for semi-persistent resourceconfiguration, a specific downlink carrier may be pre-scheduled todeliver downlink HARQ feedback for uplink transmission usingsemi-persistent transmission resources. The anchor downlink carrier(primary carrier or special carrier), which is always active, may bepre-scheduled to deliver such downlink HARQ feedback. Among multipledownlink carriers, the anchor downlink carrier (primary carrier) isattached to the user equipment at all times and is always active. Oneuser equipment may maintain a single anchor carrier.

The user equipment performs PUSCH transmission through an uplink carrier(1710). The user equipment checks whether the PUSCH transmission isperformed using semi-persistent transmission resources (1715). Here,uplink transmission using semi-persistent transmission resourcesindicates absence of an associated PDCCH. In this case, the base stationsends downlink HARQ feedback for the PUSCH transmission through adownlink carrier preset at the time of semi-persistent resourceconfiguration. Hence, when the PUSCH transmission is performed usingsemi-persistent transmission resources, the user equipment receivesdownlink HARQ feedback for the PUSCH transmission through a downlinkcarrier preset at the time of semi-persistent resource configuration(anchor carrier or primary carrier) (1720). When the PUSCH transmissionis performed without using semi-persistent transmission resources (aPDCCH directs uplink transmission), the user equipment receives downlinkHARQ feedback through a downlink carrier on which PDCCH reception foruplink transmission is performed (1725).

As described above, in the sixth embodiment, when the user equipmentperforms PUSCH transmission using semi-persistent transmission resources(without using uplink resource allocation information), it receivesdownlink HARQ feedback for the PUSCH transmission through a downlinkcarrier preset at the time of semi-persistent resource configuration.When the user equipment performs PUSCH transmission without usingsemi-persistent transmission resources, it receives downlink HARQfeedback through a downlink carrier on which PDCCH reception for uplinktransmission is performed.

Seventh Embodiment

The seventh embodiment of the present invention provides a methodwherein, when PUSCH transmission is performed using semi-persistenttransmission resources, HARQ feedback is received on a downlink carrierassociated in path loss with the uplink carrier in which thesemi-persistent transmission resources are configured. Here, for uplinktransmission, the user equipment adjusts transmit power output inconsideration of path loss of a given downlink carrier.

FIG. 18A is a flowchart for UE operation according to the seventhembodiment of the present invention, and FIG. 18B is a sequence diagramfor an HARQ handling procedure between the user equipment and basestation according thereto.

Referring to FIG. 18B, the ENB sends a control message indicatingcarrier aggregation to the user equipment (1850). Here, the controlmessage contains carrier aggregation information related to downlinkcarriers and uplink carriers aggregated in the user equipment (DLcarrier information and UL carrier information). The carrier aggregationinformation may include information on unique identifiers, centerfrequencies and bandwidths of downlink carriers and uplink carriers, andfeedback relationships between downlink carriers and uplink carriers.After reception of the control message, the user equipment performsdownlink and uplink carrier configuration and monitors the PDCCH of eachdownlink carrier to receive downlink or uplink scheduling information.

The ENB sends uplink semi-persistent resource allocation informationthrough a downlink carrier (DL CC x; UL SPS resource allocation) to theuser equipment, and the user equipment receives the same (1855). Here,the uplink semi-persistent resource allocation information may containinformation specifying transmission resources to be used for downlinkfeedback (for example, information indicating transmission resources ofthe PDCCH to be used for delivering downlink feedback in response touplink traffic through the uplink semi-persistent transmissionresources: HARQ feedback resource information). Here, only transmissionresources are indicated, and the downlink carrier to deliver downlinkfeedback is not indicated.

The downlink carrier to deliver downlink HARQ feedback in response touplink traffic using uplink semi-persistent transmission resources maybe determined according to a preset criterion. For example, downlinkHARQ feedback may be received on a downlink carrier associated in pathloss with the uplink carrier in which the uplink semi-persistenttransmission resources are configured. A path loss association between adownlink carrier and an uplink carrier may be determined by the gapbetween the center frequency of the downlink carrier and that of theuplink carrier. For example, when a downlink carrier and an uplinkcarrier are separated less than a given bandwidth, they may be regardedas being associated in path loss. Alternatively, the control messageindicating carrier aggregation may contain an indication to downlink anduplink carriers associated in path loss.

After uplink semi-persistent resources are allocated, the user equipmentperforms uplink transmission at regular intervals through the allocateduplink semi-persistent resources (1860). For example, after a given timefrom reception of the uplink semi-persistent resource allocationinformation, the user equipment may perform uplink transmission throughthe uplink semi-persistent resources. After uplink transmission, theuser equipment receives downlink HARQ feedback through a transmissionresource (indicated at step 1855) of the PDCCH of a downlink carrieridentified according to a preset rule (1865).

For uplink transmission using dynamically allocated transmissionresources (not semi-persistent transmission resources), the ENB sendsdownlink HARQ feedback on a downlink carrier on which uplink resourceallocation information is sent, and the user equipment receives thesame. More specifically, the user equipment receives uplink resourceallocation information for an uplink carrier through a downlink carrier(1870). The user equipment performs uplink transmission using uplinktransmission resources of the uplink carrier (1875). The user equipmentreceives downlink HARQ feedback for uplink data through the downlinkcarrier on which the uplink resource allocation information has beenreceived (1880). That is, upon reception of PUSCH data, the ENB sendsdownlink feedback for the PUSCH data through the downlink carrier onwhich the uplink resource allocation information has been sent. AfterPUSCH transmission using allocated uplink transmission resources, theuser equipment monitors the downlink carrier on which the uplinkresource allocation information is received to receive downlinkfeedback.

Referring to FIG. 18A, which illustrates UE operation according to theseventh embodiment, after sending a control message indicating carrieraggregation (DL carrier information and UL carrier information), the ENBsends uplink semi-persistent resource allocation information through adownlink carrier (UL SPS resource allocation (HARQ feedback resourceinformation)) to the user equipment. In the seventh embodiment, downlinkHARQ feedback may be received on a downlink carrier associated in pathloss with the uplink carrier in which the uplink semi-persistenttransmission resources are configured. The user equipment identifies apath loss association between downlink carries and uplink carriers(1805). Here, the user equipment identifies mappings between downlinkcarries and uplink carriers, and information on the mappings may beprovided to the user equipment using an RRC control message during acall setup procedure.

The user equipment performs PUSCH transmission through an uplink carrier(1810). The user equipment checks whether the PUSCH transmission isperformed using semi-persistent transmission resources (1815). Here,uplink transmission using semi-persistent transmission resourcesindicates absence of an associated PDCCH. When the PUSCH transmission isperformed using semi-persistent transmission resources, the userequipment receives downlink HARQ feedback for the PUSCH transmissionthrough a downlink carrier associated in path loss with the uplinkcarrier on which the PUSCH transmission is performed using thesemi-persistent transmission resources (1820). The user equipment mayalso receive downlink HARQ feedback through a downlink carrier having afeedback relationship with the uplink carrier on which PUSCHtransmission is performed using the semi-persistent transmissionresources. When the PUSCH transmission is performed without usingsemi-persistent transmission resources (a PDCCH directs uplinktransmission), the user equipment receives downlink HARQ feedbackthrough a downlink carrier on which PDCCH reception for uplinktransmission is performed (1825).

Eighth Embodiment

The eighth embodiment of the present invention provides a methodwherein, when PUSCH transmission is performed using semi-persistenttransmission resources, HARQ feedback is received on a downlink carrierthrough which a signal activating the semi-persistent transmissionresources has been received. After receiving a signal activatingsemi-persistent transmission resources through the PDCCH, the userequipment periodically performs PUSCH transmission through the activatedsemi-persistent transmission resources. That is, when performing PUSCHtransmission through separate semi-persistent transmission resources,the user equipment receives HARQ feedback on a downlink carrier throughwhich a signal activating the semi-persistent transmission resources hasbeen received.

FIG. 19 is a flowchart illustrating UE operation according to the eighthembodiment of the present invention.

Referring to FIG. 19, the user equipment receives a signal activatinguplink semi-persistent transmission resources through a downlink carrier(1905). The signal for uplink semi-persistent resource activation hasthe same format as a regular signal for uplink resource allocation, andactivates allocated semi-persistent transmission resources in a givencycle. The user equipment retains information on the downlink carrierthrough which the signal for uplink semi-persistent resource activationis received to handle downlink HARQ feedback in response to uplinktransmission using semi-persistent transmission resources.

The user equipment performs PUSCH transmission through an uplink carrier(1910). The user equipment checks whether the PUSCH transmission isperformed using semi-persistent transmission resources (1915). Here,uplink transmission using semi-persistent transmission resourcesindicates absence of a signal for uplink transmission resourceallocation associated with the uplink transmission. When the PUSCHtransmission is performed using semi-persistent transmission resources,the user equipment identifies the downlink carrier through which thesignal for uplink semi-persistent resource activation is received andreceives downlink HARQ feedback for the PUSCH transmission through theidentified downlink carrier (1920). When the PUSCH transmission isperformed without using semi-persistent transmission resources (a signalfor dynamic uplink resource allocation is present), the user equipmentreceives downlink HARQ feedback through a downlink carrier on which thesignal for dynamic uplink resource allocation is received (1925).

Ninth Embodiment

The ninth embodiment of the present invention provides a method wherein,when PUSCH transmission is performed on an uplink carrier, the userequipment receives HARQ feedback on a downlink carrier selectedaccording to the same criterion regardless of whether the uplinktransmission is conducted through transmission resources dynamicallyallocated by the PDCCH or through semi-persistent transmissionresources.

In the ninth embodiment, the base station establishes relationshipsbetween downlink carriers and uplink carriers aggregated in one userequipment according to an uplink scheduling perspective. Uplink resourceallocation information for an uplink carrier and HARQ feedback foruplink transmission are transmitted only on a downlink carrier relatedin uplink scheduling perspective with the uplink carrier. Relationshipsin uplink scheduling perspective may be determined by the base stationand be notified to the user equipment during a call setup procedure.When the user equipment identifies a downlink carrier related in uplinkscheduling perspective with an uplink carrier, it receives HARQ feedbackon the identified downlink carrier in response to uplink data sentthrough the uplink carrier.

FIG. 20 is a flowchart illustrating UE operation according to the ninthembodiment of the present invention.

Referring to FIG. 20, the user equipment receives information regardingrelationships in uplink scheduling perspective between downlink carriersand uplink carriers from the base station (2005). This informationindicates a downlink carrier related in uplink scheduling perspectivewith a given uplink carrier. When a downlink carrier is related inuplink scheduling perspective with an uplink carrier, uplink resourceallocation information for the uplink carrier and HARQ feedback foruplink transmission through the uplink carrier are transmitted only onthe related downlink carrier.

The user equipment performs PUSCH transmission through an uplink carrier(2010). The user equipment identifies a downlink carrier related inuplink scheduling perspective with the uplink carrier on which the PUSCHtransmission is performed (2015). Later, the user equipment receivesHARQ feedback through the downlink carrier related in uplink schedulingperspective (2020). For reference, in most existing methods, downlinkHARQ feedback in response to uplink transmission is received through adownlink carrier on which uplink resource allocation information for theuplink transmission is performed. If a downlink carrier for HARQfeedback is selected as in the existing methods, it is difficult todetermine a downlink carrier for receiving HARQ feedback when separateuplink resource allocation information is not present as in the case ofsemi-persistent resource allocation. In contrast, in the method of theninth embodiment, relationships in uplink scheduling perspective betweendownlink carriers and uplink carriers are established in advance. Later,HARQ feedback in response to uplink transmission through an uplinkcarrier is received through a downlink carrier related in uplinkscheduling perspective with the uplink carrier on which the uplinktransmission is conducted. Hence, the downlink carrier to receive HARQfeedback can be clearly determined even in the case of uplinktransmission using semi-persistent transmission resources.

FIG. 21 is a block diagram of the user equipment having a carrieraggregation capability according to another embodiment of the presentinvention.

Referring to FIG. 21, the user equipment may include a transceiver unit2105, an HARQ feedback carrier determiner 2115, a control unit 2110, amux/demux unit 2120, a control message handler 2135, and higher layerunits 2125 and 2130.

The transceiver unit 2105 receives data and control signals from a basestation through a downlink carrier and sends data and control signals tothe base station through an uplink carrier. When carrier aggregation isutilized, the transceiver unit 2105 may send and receive data andcontrol signals through multiple downlink carriers and uplink carriers.

The control unit 2110 controls the transceiver unit 2105 to send uplinktraffic or to receive downlink traffic according to a received controlsignal (such as uplink or downlink resource allocation information). Thecontrol unit 2110 notifies the HARQ feedback carrier determiner 2115 ofa downlink carrier on which uplink or downlink resource allocationinformation is received and downlink and uplink carriers scheduled fortransmission.

The HARQ feedback carrier determiner 2115 identifies uplink and downlinkfeedback relationships on the basis of information on relationshipsbetween downlink carriers and uplink carriers provided by the controlmessage handler 2135. The HARQ feedback carrier determiner 2115determines, in response to downlink traffic (uplink traffic), an uplinkcarrier (a downlink carrier) to be used to send (receive) HARQ feedbackon the basis of information provided by the control unit 2110, andcontrols the transceiver unit 2105 to send (receive) HARQ feedbackthrough the determined uplink carrier (downlink carrier).

In the third embodiment of the present invention, the HARQ feedbackcarrier determiner 2115 controls the transceiver unit 2105 to receive,in response to uplink transmission on an uplink carrier, downlink HARQfeedback on a downlink carrier through which downlink resourceallocation information for the uplink transmission is received. In thesixth embodiment, the HARQ feedback carrier determiner 2115 controls thetransceiver unit 2105 to receive, in response to uplink transmissionperformed using semi-persistent transmission resources, downlink HARQfeedback through a preset downlink carrier such as the primary downlinkcarrier. In the seventh embodiment, the HARQ feedback carrier determiner2115 controls the transceiver unit 2105 to receive, in response touplink transmission performed using semi-persistent transmissionresources, downlink HARQ feedback through a downlink carrier associatedin path loss with the uplink carrier in which the semi-persistenttransmission resources are configured.

The mux/demux unit 2120 multiplexes data coming from the higher layerunits 2125 and 2130 or the control message handler 2135, anddemultiplexes data received by the transceiver unit 2105 and forwardsthe demultiplexed data to the higher layer units 2125 and 2130 or thecontrol message handler 2135.

The control message handler 2135 processes a control message receivedfrom the network and performs a corresponding operation. For example,the control message handler 2135 forwards information on the uplink ordownlink feedback relationship contained in a control message to theHARQ feedback carrier determiner 2115. Specifically, as described inconnection with the first to ninth embodiments, the control messagehandler 2135 analyzes a received control message to identify an uplinkor downlink feedback relationship and forwards the analysis results tothe HARQ feedback carrier determiner 2115. The higher layer units 2125and 2130 may be configured on a service basis. The higher layer units2125 and 2130 delivers user data generated by user applications such asFTP and VoIP to the mux/demux unit 2120, and delivers data coming fromthe mux/demux unit 2120 to appropriate user applications at the higherlayer.

To describe the operation of the user equipment having the aboveconfiguration, the transceiver unit 2105 receives and transmits data andcontrol signals through multiple carriers when carrier aggregation isenabled. The transceiver unit 2105 receives data and control signalsfrom the base station through a downlink carrier. The control unit 2110controls the transceiver unit 2105 to send uplink traffic or to receivedownlink traffic according to a received control signal such as uplinkor downlink resource allocation information. Here, the mux/demux unit2120 demultiplexes data received by the transceiver unit 2105 andforwards the demultiplexed data to the higher layer units 2125 and 2130or the control message handler 2135, and multiplexes signals coming fromthe higher layer units 2125 and 2130 or the control message handler 2135and forwards the multiplexed signal to the transceiver unit 2105.

The control message handler 2135 processes a control message receivedfrom the network and performs a corresponding operation. For example,the control message handler 2135 forwards information on the uplink ordownlink feedback relationship contained in a control message to theHARQ feedback carrier determiner 2115. The HARQ feedback carrierdeterminer 2115 identifies uplink and downlink feedback relationships onthe basis of information on relationships between downlink carriers anduplink carriers provided by the control message handler 2135.

The control unit 2110 notifies the HARQ feedback carrier determiner 2115of a downlink carrier on which uplink or downlink resource allocationinformation is received and downlink and uplink carriers scheduled fortransmission. The HARQ feedback carrier determiner 2115 determines, inresponse to downlink traffic (uplink traffic), an uplink carrier (adownlink carrier) to be used to send (receive) HARQ feedback on thebasis of the information provided by the control unit 2110, and controlsthe transceiver unit 2105 to send (receive) HARQ feedback through thedetermined uplink carrier (downlink carrier).

While the present invention has been described with reference toexemplary embodiments thereof, it will be clear to those of ordinaryskill in the art to which the invention pertains that variousmodifications may be made to the described embodiments without departingfrom the spirit and scope of the invention as defined in the appendedclaims and their equivalents.

The invention claimed is:
 1. A method by a terminal, the methodcomprising: receiving uplink resource allocation information on a firstuplink carrier of a first cell via a second downlink carrier of a secondcell, the first cell including the first uplink carrier and a firstdownlink carrier; transmitting uplink data based on the uplink resourceallocation information via the first uplink carrier; and receivingfeedback information corresponding to the uplink data via the seconddownlink carrier of the second cell.
 2. The method of claim 1, furthercomprising monitoring the second downlink carrier via which the uplinkresource allocation information is received.
 3. The method of claim 1,wherein the uplink data corresponds to a physical uplink shared channel(PUSCH) data and the feedback information corresponds to an hybridautomatic repeat request (HARQ) ack/nack for the PUSCH data.
 4. Themethod of claim 1, wherein the first uplink carrier and the firstdownlink carrier are associated with a first frequency, and wherein thesecond downlink carrier is associated with a second frequency.
 5. Themethod of claim 1, wherein the first cell and the second cell areconfigured to the terminal for a carrier aggregation.
 6. A terminalcomprising: a transceiver configured to transmit and receive a signal;and a controller coupled with the transceiver and configured to: receiveuplink resource allocation information on a first uplink carrier of afirst cell via a second downlink carrier of a second cell, the firstcell including the first uplink carrier and a first downlink carrier,transmit uplink data based on the uplink resource allocation informationvia the first uplink carrier, and receive feedback informationcorresponding to the uplink data via the second downlink carrier of thesecond cell.
 7. The terminal of claim 6, wherein the controller isfurther configured to monitor the second downlink carrier via which theuplink resource allocation information is received.
 8. The terminal ofclaim 6, wherein the uplink data corresponds to a physical uplink sharedchannel (PUSCH) data, and wherein the feedback information correspondsto a hybrid automatic repeat request (HARQ) ack/nack for the PUSCH data.9. The terminal of claim 6, wherein the first uplink carrier and thefirst downlink carrier are associated with a first frequency, andwherein the second downlink carrier is associated with a secondfrequency.
 10. The terminal of claim 6, wherein the first cell and thesecond cell are configured to the terminal for a carrier aggregation.11. A method by a base station, the method comprising: transmittinguplink resource allocation information on a first uplink carrier of afirst cell via a second downlink carrier of a second cell, the firstcell including the first uplink carrier and a first downlink carrier;receiving uplink data based on the uplink resource allocationinformation via the first uplink carrier; and transmitting feedbackinformation corresponding to the uplink data via the second downlinkcarrier of the second cell.
 12. The method of claim 11, wherein thefeedback information is transmitted via a cell which the uplink resourceallocation information is transmitted.
 13. The method of claim 11,wherein the uplink data corresponds to a physical uplink shared channel(PUSCH) data, and wherein the feedback information corresponds to ahybrid automatic repeat request (HARQ) ack/nack for the PUSCH data. 14.The method of claim 11, wherein the first uplink carrier and the firstdownlink carrier are associated with a first frequency, and wherein thesecond downlink carrier is associated with a second frequency.
 15. Themethod of claim 11, wherein the first cell and the second cell areconfigured to a terminal for a carrier aggregation.
 16. A base stationcomprising: a transceiver configured to transmit and receive a signal;and a controller coupled with the transceiver and configured to:transmit uplink resource allocation information on a first uplinkcarrier of a first cell via a second downlink carrier of a second cell,the first cell including the first uplink carrier and a first downlinkcarrier, receive uplink data based on the uplink resource allocationinformation via the first uplink carrier, and transmit feedbackinformation corresponding to the uplink data via the second downlinkcarrier of the second cell.
 17. The base station of claim 16, whereinthe feedback information is transmitted via a cell which the uplinkresource allocation information is transmitted.
 18. The base station ofclaim 16, wherein the uplink data corresponds to a physical uplinkshared channel (PUSCH) data, and wherein the feedback informationcorresponds to a hybrid automatic repeat request (HARQ) ack/nack for thePUSCH data.
 19. The base station of claim 16, wherein the first uplinkcarrier and the first downlink carrier are associated with a firstfrequency, and wherein the second downlink carrier is associated with asecond frequency.
 20. The base station of claim 16, wherein the firstcell and the second cell are configured to a terminal for a carrieraggregation.